1. FIELD OF THE INVENTION
The present invention relates to a picolinic acid derivative and a salt thereof, and a herbicidal composition containing the same as an active ingredient, which is applicable to a paddy field, an upland filed and a non-agricultural land.
2. DISCUSSION OF BACKGROUND
As a herbicide having a structure similar to the compound of the present invention, a 3-(4,6-dimethoxypirimidin-2-yl)oxypicolinic acid derivative has been known (Japanese Unexamined Patent Publication No. 121973/1990). This publication discloses a picolinic acid type (2-pyridine-carboxylic acid) structure and an isonicotinic acid type (4-pyridine-carboxylic acid) structure as a compound having a pyridine ring. However, this publication does not disclose a compound having a substituent on the pyridine ring, like the compound of the present invention. Accordingly, there is no specific disclosure or suggestion of the herbicidal effects of such a compound.
Further, it is also known that a 2-sulfoneaminopyrimidine derivative has herbicidal activities (Japanese Unexamined Patent Publication No. 149567/1990). However, in this case, a large dose is required to control various weeds simultaneously, and its herbicidal effects are not yet satisfactory.
Furthermore, a similar patent publication (WO-9207846-Al) discloses herbicidal effects of an amino group derivative at the 6-position of picolinic acid. However, there is no specific description about the safety of the compound to crop plants, and the herbicidal effects are not satisfactory particularly to control weeds in an agricultural field.
In recent years, a number of herbicides have been developed and practically used, and they have contributed to the saving of energy for the agricultural operations and to the improvement of the production efficiency. However, in their practical use, such herbicides have various problems with respect to the herbicidal effects and the safety to the crop plants. For example, perennial weeds such as Johnsongrass are widely distributed throughout agricultural fields in the world and regarded as weeds which are very difficult to control. Under the circumstances, it is desired to develop an improved herbicide.